#13090: Make LinearCode take minimum distance as a parameter
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Reporter: ppurka | Owner: wdj
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-5.1
Component: coding theory | Resolution:
Keywords: minimum distance | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Changes (by ppurka):
* status: new => needs_review
Old description:
> For some codes, the minimum distance is a known parameter. For instance,
> for Reed-Solomon code, Hamming code, Golay code, etc. For these cases,
> making Sage compute the minimum distance is quite a wasted effort.
>
> I am introducing a patch which does the following
> 1. adds an extra parameter `d=None` to `LinearCode`. If `d` is provided,
> then the minimum distance of the code is set to `d`.
> 2. An extra attribute `self.__distance` is introduced which stores the
> distance. If `d` is not provided during the initialization of the class
> and if the minimum distance has already been computed before, then the
> computed value is stored in `d` so that it does not need to be recomputed
> the next time it is called.
> 3. To force recomputation of the distance, if desired,
> `LinearCode.minimum_distance()` takes the parameter `algorithm="gap"`.
New description:
For some codes, the minimum distance is a known parameter. For instance,
for Reed-Solomon code, Hamming code, Golay code, etc. For these cases,
making Sage compute the minimum distance is quite a wasted effort.
I am introducing a patch which does the following
1. adds an extra parameter `d=None` to `LinearCode`. If `d` is provided,
then the minimum distance of the code is set to `d`.
2. An extra attribute `self.__distance` is introduced which stores the
distance. If `d` is not provided during the initialization of the class
and if the minimum distance has already been computed before, then the
computed value is stored in `d` so that it does not need to be recomputed
the next time it is called.
3. To force recomputation of the distance, if desired,
`LinearCode.minimum_distance()` takes the parameter `algorithm="gap"`.
To see why the patch can be useful, note the long time it takes to (force)
compute the distance on a relatively small code:
{{{
sage: C = ReedSolomonCode(15,6,GF(16,'a'))
sage: %time C.minimum_distance()
CPU times: user 0.00 s, sys: 0.00 s, total: 0.00 s
Wall time: 0.00 s
10
sage: %time C.minimum_distance(algorithm='gap') # forcing computation of
distance
CPU times: user 0.25 s, sys: 0.04 s, total: 0.29 s
Wall time: 8.55 s
10
}}}
----
Apply [attachment:trac_13090-minimum_distance.patch] to `devel/sage`.
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13090#comment:1>
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